Как вставить в шифр цезаря генератор псевдослучайных чисел? - Visual Basic .NET

Public Class Form1
    Const sdvig As Integer = 3
    Private Function cs(ByVal s As String, ByVal sdvig As Integer) As String
        Dim i As Integer
        cs = ""
        For i = 1 To Len(s)
            cs &= cc(Mid(s, i, 1), sdvig)
        Next
    End Function
 
    Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
        Label3.Text = cs(TextBox1.Text, sdvig)
 
    End Sub
 
    Private Function cc(ByVal c As Char, ByVal sdvig As Integer) As String
        cc = ""
        If Asc(c) <> 0 Then Return Chr((Asc(c) + sdvig) Mod 255)
    End Function
End Class